1. Field of the Invention
The present invention is directed to a method and apparatus for controlling the compression force in an x-ray apparatus for mammographic examinations, of the type wherein a breast under examination is compressed with increasing force between a pressure plate and a support platform.
2. Description of the Prior Art
For good image quality in radiographic examinations of a breast, it is known that optimal compression of the breast is necessary to minimize the amount of secondary radiation from breast tissue. Such secondary radiation impairs image quality, and decreases with decreasing breast thickness.
A known procedure for compressing a breast under examination is described European Application 0 435 837 wherein the compression force increases as the pressure plate is advanced at a uniform speed to a preset position, with the pressure plate thereafter being advanced at a decreasing speed until a predetermined, non-variable end value of the compression force is reached. A disadvantage of this procedure is that the preset end value is not adapted to all breast sizes, and can therefore result in a compression force, exerted by the plate against the breast, which is too large or too small. In the case of a small breast, the patient may experience pain caused by excessive compression of the breast, but the compression force may not be large enough to generate a satisfactory image quality with a large breast.